Reduced mobility is one of the most debilitating consequences of vision loss for more than three million Americans with low vision. We define visual accessibility as the use of vision to travel efficiently and safely through an environment, to perceive the spatial layout of key features in the environment, and to keep track of one's location in the environment. Our long-term goal is to create tools to enable the design of safe environments for the mobility of low-vision individuals and to enhance safety for the elderly and others who may need to operate under low lighting and other visually challenging conditions. We plan to develop a computer-based design tool in which environments (such as a hotel lobby, large classroom, or hospital reception area), could be simulated with sufficient accuracy to predict the visibility of key landmarks or obstacles, such as steps or benches, under differing lighting conditions. Our project addresses one of the National Eye Institute's program objectives: "Develop a knowledge base of design requirements for architectural structures, open spaces, and parks and the devices necessary for optimizing the execution of navigation and other everyday tasks by people with visual impairments". Our research plan has four specific goals: 1) Develop methods for predicting the physical levels of light reaching the eye in existing or planned architectural spaces. 2) Acquire performance data for normally sighted subjects with visual restrictions and people with low vision to investigate perceptual capabilities critical to visually-based mobility. 3) Develop models that can predict perceptual competence on tasks critical to visually-based mobility. 4) Demonstrate a proof-of-concept software tool that operates on design models from existing architectural design systems and is able to highlight potential obstacles to visual accessibility. The lead investigators in our partnership come from three institutions: University of Minnesota Gordon Legge, Daniel Kersten;University of Utah William Thompson, Peter Shirley, Sarah Creem-Regehr;and Indiana University Robert Shakespeare. This interdisciplinary team has expertise in the four areas required for programmatic research on visual accessibility empirical studies of normal and low vision (Legge, Kersten, Creem-Regehr, and Thompson), computational modeling of perception (Legge, Kersten, and Thompson), photometrically correct computer graphics (Shirley), and architectural design and lighting (Shakespeare).